Study of Space Charge Behavior in Polyethylene for Power Cable Insulation by Laser-Induced-Pressure-Pulse Technique Effects of the Interfece with Semiconducting Layer and Antioxidant

Abstract

We have been investigating the effects of antioxidant on the space-charge behavior in low-density polyethylene (LDPE) for cable insulation by utilizing laser-induced-pressure-pulse (LIPP) technique. In the present study, we studied the effects of antioxidant in PE in contact with a semiconducting layer. Results obtained are as follows. 1) In LDPE without antioxidant and with a semiconducting layer, negative and positive carrier injections from the semiconducting layer are enhanced, and injected carriers easily travel in the bulk. This results in the uniform space-charge formations in the PE bulk. 2) In LDPE with antioxidant and with a semiconducting layer, remarkable negative and positive homo space-charge formations in the vicinity of the iraterface are observed. These lead to the remarkable field distortion of about 60‰ of applied average field at the interface. The profile of the negative homo space charge is almost independent of the applied field and the sample thickness, i. e. its centroid is about 20μm deep from the interface. This is possibly due to carrier trapping. The profile of the positive homo space charge depends on the applied field and the sample thickness, i. e. it extends deeper in the bulk with increasing applied field and decreasing sample thickness. These remarkable homo space-charge formations in the vicinity of the interface arise from the coexistence of antioxidant and the semiconducting layer. 3) Space-charge behavior in XLPE with antioxidant and with a semiconducting layer is similar to that in LDPE with antioxidant. It suggests that antioxidant is more effective on space-charge behavior than cross-linking.